Plants on land areas experience extreme environmental conditions, such as variations in air temperature, wind speed, light levels, relative humidity and available nutrients and water. Increasing foliage reflectance is recognized as a means of moderating environmental conditions leading to such conditions as heat stress and sunburn on plants. Reflective coatings may be applied to the surfaces of fruits and vegetables to reduce excessive heat and light (including ultraviolet and infrared light) at the fruit/vegetable surface in an attempt to prevent “sunburn.” Sunburn appears as a darkened area on the surface of fruits and vegetables. Beneath the sunburned area, the fruit/vegetable tissue is damaged and likely to develop disease symptoms. The strategy of applying a reflective treatment is to reduce the temperature of the fruit by reflecting heat or by blocking light.
However, many of the methods known in the art to increase reflectance of foliage cause decreased transpiration and decreased photosynthesis. Photosynthesis and transpiration are necessary for the plant to grow and/or produce a useful crop. Other methods for reducing environment stress on plants are described in U.S. Pat. No. 6,069,112, 6,156,327, 6,027,740 and 5,908,708. These patents describe and include methods and compositions comprising heat treated particulate materials including heat treated kaolin.
Talc is a naturally hydrophobic mineral and resists wetting by water. The hydrophobicity of talc would be an advantage for reflective compositions for plants. Once present as a film on a plant surface, talc is predicted to resist removal by water, present in the form of rain, irrigation, humidity and the like. Thus, a reflective layer of talc on a surface of a plant would be predicted to be more long lasting than a similar hydrophilic reflective layer. Thus, it is desirable to form a talc layer on plant surfaces. However, wetting talc with water to create a slurry for application to plants can be difficult. Talc placed in water exhibits a slow makedown, i.e. delayed suspension upon addition of water to form a slurry, and also exhibits clearing, i.e. settling of a slurry into a sediment resulting in a supernatant fluid layer that has been cleared of talc thus appearing clear to the eye. These properties can be troublesome to a user attempting to create a slurry of talc in water in that creating a slurry is more time-consuming, and the slurry needs more agitation in order to be effective. Another problem for the user is the problem of a “hard heel” or the development of a sediment that resists resuspension. Such a hard heel is also disadvantageous because the hard heel may be difficult to remove from spraying equipment and may clog lines.
Accordingly, there remains a need in the art for methods and compositions that protect plants and crops from environmental stresses such as sunburn while enhancing the ease of application for the user. For example, conventional treatments for protecting crop plants include the use of reflectant particles which are supplied as a powder to the user. Generally, application of a powder to the plant is not commercially practical on a large scale due to drift and inhalation hazards. Instead, the product must be applied as a slurry. However, the user may experience inconvenience and hazards associated with handling a powder during the process of preparing a slurry. Powders are messy. Powders can easily spill and are difficult to completely remove. They may aerosolize and enter the air, causing an inhalation hazard to the worker and to any others nearby. There also remains a need in the art for crop protectant compositions and methods that minimize or prevent user's exposure to dusts and powders, yet retain their ability to go into an aqueous suspension or “slurry.” There also remains a need in the art for crop protectant compositions and methods that readily wet plant surfaces and that can be removed by simple washing.
There also remains a need in the art for crop protectant compositions and methods that utilize materials that are “natural” or organic, i.e. compositions and methods that are compatible with the production and handling of organic crops and organic processed food products, as defined by the United States Department of Agriculture under the 1990 Organic Foods Production Act.